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Old Dec 13, 2009, 06:54 PM
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Skunk Water, Rhode Island
Joined Jul 2002
13,006 Posts
I had issues with the cure time, Dan. Possibly only because I was in Fla(WPB) at the time and they inject ammonia in the water system, every 3 days. So I never took the chance again. The cure would not happen till the ammonia evaporated.

Hydrocal is a Gypsum. 10x stronger than plaster of paris, but same family. It comes in casting and lay-up varieties. Smaller amounts can be had(1/2 gal) at hobby shops that deal in model railroading. Comes in a 1/2gal milk container, yellow.
It cures as does all gypsum/cement products. There is a working time, depending on viscosity of blend. Clean work tools immediately. After cure water does not harm it, like plaster of paris. With this in mind, waxing the hydrocal mold and spraying with PVA is all that is needed. I learned long ago not to epoxy Hydrocal. I wish I could have known you were doing this, Dan. The epoxy may not remain permenant. Not too much sticks to this stuff for long.

Dan, keep that 50# bag well sealed. Wrap it in double plastic bags. With you living in the south, the humidity will cause it to cure, like cement.

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Last edited by St. Martin; Dec 13, 2009 at 06:59 PM. Reason: added coments
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